Antibiotic selenomycin

ABSTRACT

An antibiotic substance, selenomycin, is produced by cultivation of Streptosporangium brasiliense n. sp. ATCC 21,393 and can be isolated from the fermentation medium by extraction. The antibiotic is active against various Gram positive bacteria.

United States Patent Coronelli et al.

[54] ANTIBIOTIC SELENOMYCIN [72] Inventors: Carolina Coronelli, 4,Piazza Novelli, Milan; Josef Thiemann, 14 V. 1e Vittorio Veneto, AppianoGentile,

Come, both of Italy [22] Filed: June 10, 1970 [21] Appl. No: 45,227

[52] US. Cl ..424/119, 195/80 [51] Int. Cl. ..A6lk 21/00 [58] Field ofSearch ..424/1 19; 195/80 [56] References Cited UNITED STATES PATENTS3,467,751 9/ 1969 Bromer et al ..424/ 1 19 51 Aug. 8, 1972 3,551,56112/1970 AszaLosetal. ..424/119 Primary Examiner-Jerome D. GoldbergAttorney-Griswold & Burdick, Kenneth C. Jork and Maynard R. Johnson [57]ABSTRACT An antibiotic substance, selenomycin, is produced bycultivation of Streptosporangium brasiliense n. sp. ATCC 21,393 and canbe isolated from the fermentation medium by'extraction. The antibioticis active against various Gram positive bacteria.

4 Claims, 2 Drawing Figures 1 ANTIBIOTIC SELENOMYCIN BRIEF SUMMARY OFTHE INVENTION This invention is directed to a novel antibiotic substanceand is particularly directed to an antibiotic substance, hereinafterreferred to as selenomycin, and is inclusive of a method for preparingthe same. The antibiotic substance selenomycin is a solid havingcharacteristic properties such as infrared absorption spectra, meltingpoints, and the like, and forming an acetyl derivative, hereinafterreferred to as acetylselenomycin, as set out in greater detail below.

Selenomycin can be prepared by cultivation of Streptosporangiumbrasiliense n. sp. in an aqueous medium and can be isolated from themedium by conventional procedures. Acetylselenomycin can be prepared byacetylation of selenomycin by conventional procedures, such as thereaction of selenomycin with acetic anhydride in a pyridine reactionmedium. In the preparation of selenomycin, the organismStreptosporangium brasiliense n. sp. is cultivated under aerobicconditions in an aqueous nutrient medium suitable for the growth of saidorganism, the medium containing a source of carbon, a source of nitrogenand inorganic salts. Cultivation is continued under conditions conduciveto the growth of said organism for a time sufficient for the productionof selenomycin, as indicated, for example by substantial antibioticactivity of the fermentation medium against Gram positive bacteria.Selenomycin thus produced can be isolated by conventional proceduressuch as removal of mycelium by centrifugation followed by extraction,typically with an organic liquid in which selenomycin is soluble andwhich is immiscible with the aqueous medium.

The antibiotic substance of the invention is useful as an antibiotic,particularly against Gram positive bacteria. Thus selenomycin can beemployed in controlling such microorganisms in conventional procedures,such as by application of an antimicrobial amount of selenomycin or acomposition containing the same to Gram positive bacteria, or tosubstrates susceptible to attack by such organisms. In addition,antimicrobial amounts of the antibiotic substance of the invention canbe administered to animals by conventional procedures in combatting Grampositive bacteria attacking said animals. Selenomycin can, for example,be employed prophylactically, by internal administration to mammalssusceptible to infection by Gram positive bacteria, or therapeutically,by internal administration to infected animals.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings illustratefeatures of the invention as follows:

FIG. 1 illustrates the infrared absorption spectrum of selenomycin; and

FIG. 2 illustrates the infrared absorption spectrum ofacetylselenomycin.

DETAILED DESCRIPTION OF THE INVENTION 1. Description ofStreptosporangium brasiliense Most of the antibiotics so far describedhave been produced by the genera Streptomyces, Micromonospora andNocardia. During the study for the isolation of new antibiotics from thegenus Streptosporangium, a new microorganism has been isolated from asoil sample received from Brazil, producing an antibiotic complex activein vitro and in vivo against several Gram positive bacteria. From thecomplex many fractions have been isolated, of which one has been foundto possess practically the whole of the activity, and which has beennamed selenomycin. The new microorganism has been given the nameStreptosporangium brasiliense n. sp. and has been deposited with theAmerican Type Culture Collection under the Ser. No. 21,393.

To investigate the growth characteristics of Streptosporangiumbmriliense, the culture was grown on a variety of culture media,incubated at 28-29 C for up to three weeks, when the final culturalexaminations were made. Most of the procedures used in the taxonomicstudy were those recommended by Shirling and Gottlieb. Generalcharacteristics: The culture grows most abundantly on oatmeal agar. Onthis medium, individual colonies attain a diameter of 5 to 6 millimetersand are covered with abundant white aerial mycelium, which, whensporangia formation is completed, assumes a light rose color.

Iodinin like crystals, common to some Streptosporangium speciesdescribed, are not formed by this culture. On some culture media, mainlyon soil agar, incomplete sporangia are formed in which more or lesstightly coiled spirals are devoid of a sporangial wall.

Optimum temperature for development was found to be 28-32 C.

Morphology of the aerial mycelium: Microscopic examination of the aerialmycelium revealed it to be formed of short highly branched hyphae, onthe tip of which a spherical sporangium develops. The average diameterof the aerial mycelium is 0.9 1.0 microns. The sporangia are quitevariable in size, generally from 3.5 to 11 microns in diameter, however,in fully matured cultures the average diameter is 12 microns. Thesporangiophore is rather short, 6 to 24 microns, with an average lengthof 15 microns and a diameter equal to that of the aerial mycelium. Thesporangiophores are disposed in a regular coiled fashion in the interiorof the sporangium. Most of the sporangiophores are cylindrical, alwaysnon-motile, measuring 2.3 to 2.8 microns by 1.1 microns, butoccasionally spherical ones with an average diameter of 1.1 microns arealso found. Arthrospore-like spores are formed, however, on the coiledhypha which are not enveloped by a visible sporangial wall, a situationoccurring rather frequently on certain poor media such as soil agar.These fragmentation spores normally measure 3.2 to 3.5 microns by 1.0micron.

Cultural and Physiological Characteristics: The cultural andphysiological characteristics of the strain are listed respectively inTables I, 2 and 3.

On most media, the vegetative mycelium was of a light cream color, withwhite aerial mycelium which became very light rose colored where intenseformation of sporangia had occurred.

Analysis performed on the purified cell-wall of the new strain showed itto be of the type 1 l" of Lechevalier.

Judging from all the mentioned characteristics it SP: None must beconcluded that the new strain belongs to the G1 2m? cream glenusstrepttgsglorzngium since, according to the key to Tmges, {white t egenera o e amily Actinoplanaceae the sporan- 5P1 None Hickey andTresners agar G: Good, wrinkled, cream to giospores are non-motile. 5amber color AM: White TABLE 1 SP: None Bennett agar G: Good, wrinkled,cream to Cultural Characteristics of Streptosporangium AM l'fi gbrasiliense l p; None n. sp. (G: growth; AM: aerial mycelium;

l l SP so ub e pigment) TABLE 2 l5 Physiological properties ofStreptosporangium Medium n. 2 G: Good, with wrinkled surb ili face;cream to light yel- (Shirling and Gottlieb) low AM: Powdery, white, rosecol- Tests Results ored zones at the colony margin None Solubilizatlonof the calcium malate glegative Nitrate reduction ositive Oatmeal agarG. S5316 surface, hya- Tyrosipase prodqcfion Negaqve (Medium n. 3,Shirling AM: Abundant, powdery, white and Gomiab) None Hydrolysis ofstarch gositlve H 8 formation ositive Starch'agar gi 53 and Liquefactionof gelatine Positive (Medium n. 4; Shirling AM: Traces, whitepeptomzation and Gottlieb) SP. None Casein h drol is Positive Glycerolasparagine agar G: Moderate, smooth surface, y ys hyaline (Medium n. 5;Shirling AM: White and Gottlieb) SP: None Peptone-yeast extract- G:Good, smooth; light yeliron agar low TABLE 3 AM: None l e gu Shirling5P1 None Utilization of carbon sources an ott ie Tyrosine agar G:tltllggiliilzlle, smooth and thin, Carbon Source Response (Medium n. 7;Shirling AM: White and Gottlieb) SP: None Inosiml Glucose asparagineagar G: Moderate, smooth, hyaline Fructose AM: Traces, white RhamnoseSP: None Mannitol Nutrient agar G: Good, slightly wrinkled, xylose creamcolor Ran-nose AM: None Arabinose SP: None Cellulose Potato agar G:Good, smooth, cream color Sucrose Q hght Yellow Glucose (positivecontrol) 5 3 518 7056 Color No carbon (negative control) one Xantineagar G: Moderate, smooth and flat,

hyaline white Strongly positlve utilization. Growth is similar to orgreater than p None growth on positive control. Calcium malate agar G:Moderate, smooth and flat, 2 Positive utilization. Growth issignificantly greater than no carbon h ali control" although somewhatless than on glucose. AM: White Utilization negative. Growth is similarto no carbon control".

TABLE 4 [Comparison to other species: Comparison of characteristics 01members of the genus Streptosporengium is set out below in Table 4.]

Physiological prop.

Width of Length of aerial Color of Starch Gelatin Nitrate Size ofsporangiomycelium, Shape and size aerial liydrolliqnereduellzS Speciessporangia, pliore, [L n of spores, u myeelium ysis faction tion formedRemarks S. ellnmi a +1 N.D. 0.7-1.0 1.0-1. 3X1. 6-1.9 White NJ).

S. amelhg slorrcnex. 6-8 N.D. 0.7-1.0 1. 0-1. 3X1. 5-1. 9 lalepink N.D.Violet crystals formed on oatmeal agar.

S. roseum. 5-9 N.D. 0. 7-1. 0 1.0-1. 3X1. 5-1. 9 Pole pink N S. rubrum 77-11. 0 1. 6-27. 0 0.8 l 1.0-1.1 Dark gray N.D.

S. viridialbum. (i-S ND 0. 7-1. 0 1. 0-1. 3X1. 6-1. 9 Grayish N.D.

white or yellowish gray. S. eulgare .1 6-8 N.D. 0.7-1. 0 1. 0-1. 3X1.5-1. 9 Pale pink", N.D. S. viridogriseum 20-48 20) 25-64 38) 0.4-0. 6 I0.2-0. 4 Light i- N.D.

greenish gray. S. brasiliensc 3. 5-14. 0 12.0) 6-24 15.0) 0. 9-1. 0 3 2.3-2.8)(1. 1 \Vhite l Spherical. Average. Cylindrical. NOTE.N.l). Notdetermined.

From the comparative data shown in Table 4 it can be seen that thestrain differs from any of the other Streptosporangium species so fardescribed. This culture is therefore a new species for which the sameStreptosporangium brasiliense n. sp., after the place of its isolation,is proposed.

2. Preparation of Selenomycin Production of selenomycin: For producingthe antibiotic selenomycin the strain Streptosporangium brasiliense isaerobically cultivated in a nutrient medium until substantial antibioticactivity is present in the medium. Selenomycin is then isolated from themedium. The nutrient medium employed is an aqueous medium containinginorganic salts, a source of carbon and of nitrogen and, if desired,growth promoting substances.

The inorganic salts employed can be, for example, alkali metal andalkaline earth metal chlorides, nitrates, carbonates, sulfates, or thesalts of magnesium, iron, manganese, zinc, etc., with the same anions.The sources of nitrogen and carbon can be, for instance, natural orsynthetic aminoacids, peptides and proteins and their hydrolysates, suchas peptone or tryptone; meat extract; the water soluble constituents ofcereal grains, such as maize or wheat; distillers solubles, yeastextract, corn steep liquor, etc., glucose, sucrose, lactose, starch,dextrins and the like.

Cultivation is carried out under aerobic conditions,

in a submerged culture, while agitating with air or oxygen at atemperature between about 25 to about 35 C., and is generally carriedout for about 24 to about 96 hours. Isolation of selenomycin: The straingrown in submerged culture produces a group of active substances. Thefollowing recovery procedure can be used to obtain selenomycin.

Selenomycin is produced in good yields and the activity can be extractedfrom the fermentation broths with an organic solvent, preferably,butanol, ethyl acetate or chloroform, the extraction being carried outwith adjustment of the broth to a slightly acidic pH. Selenomycin issomewhat unstable under acidic conditions (acid pH); thus, the pH forextraction should be carefully controlled and should not be lower than5.0.

In a preferred procedure, the fermentation broth is filtered at alkalinepH in order to avoid retention of some microbiological activity in themycelial filter cake; the filtrate is acidified to pH 5.5 and extractedtwice with chloroform; the combined extracts are concentrated to a smallvolume under reduced pressure and selenomycin is obtained by addition ofa large volume of light petroleum to the concentrated extracts toprecipitate the product. The product thus obtained can be purified bytreatment at 35 C with a mixture containing 30 percent chloroform and 70percent benzene. The insoluble fraction is filtered off and thesolution, concentrated to a small volume, is added to a large volume ofhexane to precipitate the product. The product thus obtained isdissolved in hot benzene, decolorized with charcoal, filtered and cooledat 4 C. The antibiotic is obtained as a white amorphous powder whichmelts at 135138 C.

3. Properties of Selenomycin Properties of selenomycin The antibiotic issoluble in alcohols, chloroform, ethyl acetate. acetone, dioxane and hotbenzene; insoluble in water at neutral and acidic pH, soluble inalkaline water, insoluble in diethyl ether.

The ultraviolet absorption spectrum shows the following maxima: in HCl0.1N shoulder at 245-257 mu E}Z;,,=41), in buffer solution pH 7.3 295 mu(El 88) in NaOH 0.1N 295 my '13)} ?,,=88).

The presence of a function with pKa 5.5 has been revealed by means ofspectrophotometric titration.

The infrared absorption spectrum of selenomycin in nujol mull showsabsorptions at the following frequencies: 3,400, 1,720, 1,650, 1,550,1,520, 1,350 (sh), 1,240, 1,200, 1,170, 1,100, 1,040, 980, 950, 912,870, 835, 815, 785, 770, 740, 720 cm". The infrared absorption spectrumof selenomycin is represented in FIG. 1.

Selenomycin gives positive Tollens and Fehling reactions, negativeShifi, FeCl and Molish reactions; it rapidly decolorizes potassiumpermanganate in both acidic and neutral solutions, gives aphenylhydrazone with 2,4-dinitro-phenylhydrazine, a brown color withconcentrated sulfuric acid and concentrated hydrochloric acid.

The paper chromatographic behavior of selenomycin with different solventsystems is summarized in the following Table 5:

TABLE 5 Paper Chromatographic Behavior of Selenomycin Solvent mixture Rfvalue 1 Water saturated butanol 0.84 2) Water saturated butanol+ 2%paratoluenesulfonic acid 0.95 3) Water saturated butanol 2% NH ,OH 0.694) Butanol saturated water 0.78 5) NH CI 20% aqueous solution 0.00 6)Phenol water 25% 0.96 7) Butanol: methanol: water 4:1:2

0.75 g methyl orange 0.82 8) Butanol: methanol: water 4:1:2 0.92 9)Acetone: water 1:1 0.34 10) Water saturated ethyl acetate 0.79

The antibiotic is. visualized on paper strips by microbiologicaldevelopment on agar plates seeded with B. subtilis.

Selenomycin gives an acetyl derivative acetylselenomycin by acetylationof selenomycin with acetic anhydn'de in pyridine. The derivative can beobtained in a. pure form by crystallization from methanol. Theanalytical data for the acetyl derivative are as follows:

C=55.5% H=5.86% O= 38.8% COCH =21% It melts at l52-154 C. The specificrotation is 019 34 (C 0.3 percent in methanol). The ultravioletabsorption spectrum shows maxima at 294 mp. (E23 60) in NaOH 0.1N andshoulder at 250-270 my. in HCl 0.1N and in buffer solution pH 7.3.

The infrared absorption spectrum in nujol mull shows absorption at thefollowing frequencies: 1,790, 1,750, 1,720 (sh), 1,640, 1,550, 1,240,1,195, 1,1301,040, 980, 958, 920, 865, 780, 750-720 cm. The infraredabsorption spectrum of acetylselenomycin is represented in FIG. 2.Selenomycin is stable in neutral and alkaline solution but unstable inacid solution; aqueous solutions of the antibiotic at pH 3.0 losepercent of the activity after 24 hours.

Selenomycin shows activity against various Gram positive bacteria whileit is much less active against Gram negative bacteria, yeasts and fungi.The minimal inhibitory concentrations against various microorganisms arereported in the following table 6:

TABLE 6 Antimicrobial Activity of Selenomycin Organism Staphylococcusaureus ATCC 6538 Staphylococcus aureus Tour Staphylococcus aureus ATCC9144 Staphylococcus albus ATCC 12228 Streptococcus faecalis ATCC 10541Streptococcus faecalis ATCC 7080 Streptococcus hemolyticus C 203Streptococcus agalactiae ATCC 7077 Streptococcus bovis ATCC 9809Diplococcus pneumoniae UC 41 Sarcina lutea ATCC 9341 Micrococcus flavusATCC 10240 Bacillus subtilis ATCC 6633 Bacillus cereus ATCC 10876Bacillus anthracis M 401 Clostridium perfringens ATCC 3626 Conebacterium diphtheriae mitis 0.2 AT C 11051 Proteus vulgaris 100Escherichia coli ATCC 10536 100 Pseudomonas aeruginosa ATCC 10145 100Candida albicans SKF 10231 100 Trichophyton mentagrophytes SKF 8757 100M cobacterium tuberculosis H37Rv 100 A CC 9360 Selenomycin shows aninteresting activity in controlling infections due to Staphylococcus,Streptococcus, Diplococcus and in general to Gram positive bacteria inanimals. The following ED values have been obtained on mice treatedsubcutaneously for three days with the antibiotic after having beeninfected with the following strains:

S. aureus ED 30 mg/Kg S. hemolyticus ED 20 mg/Kg D. pneumoniae ED mg/KgThe LD in mice is 400 mg/Kg by intraperitoneal route. Useful therapeuticlevels are reached by administration of 50 mg/Kg of selenomycin to miceby subcutaneous, rectal and intraperitoneal route. The blood levels aregiven in the following table 7:

TABLE 7 Blood level of selenomycin in micrograms per milliliter afteradministration of 50 mg/Kg to mice.

Hours after Route administration subcutaneous rectal intraperitonealDESCRIPTION OF PREFERRED EMBODIMENTS The following examples areillustrative of the invention but are not to be construed as limitingthe same.

EXAMPLE 1 The composition of this germination medium is the following:

Peptone 5.0 grams Meat extract 5.0 grams NaCl 5.0 grams Yeast extract1.0 grams Glucose 10.0 grams Tap water q.s. to 1 liter The medium isadjusted to pH 7.2 and sterilized for 20 minutes at 121 C. Thegermination flasks are incubated at 28 C for 72 hours on a rotary shakerhaving a 2 inch throw and operating at 240 rpm. After the aforementionedincubation time the pH of the medium is 8.5 and the percent myceliumvolume (pmv) is 12. The percent mycelium volume is determined bycentrifuging a 10 milliliter sample for 10 minutes at 3,000 rpm.

11. Fermentation conditions A 10 percent transfer is made from thegermination flask to 500 milliliter Erlenmeyer flasks provided with onelateral baffle, and containing milliliters of medium of the followingcomposition:

Meat extract 4.0 grams Peptone 4.0 grams NaCl 2.5 grams Yeast extract1.0 grams Soybean meal 10.0 grams Glucose 50.0 grams CaCO 5.0 grams Tapwater q.s. to 1 liter Microorganisms Antibiotic activity in dilutionunits (72 hours fermentation.)

Bacillus subtilis 1/2560 Staphylococcus aureus l/320 EXAMPLE 2 Aninoculum is prepared and grown as in Example 1 employing a fermentationmedium similar to that described above in Example 1 modified bysubstituting various other carbohydrates for glucose. Aliquots of thefermentation broth are assayed for antibiotic activity, using B.subtilis as indicator strain, after 72 and 96 hours of fermentation. Theresults are as follows:

Culture medium of Inhibition zones (in millimeters) Example 1 with ofB.subtilis, using standard 9 mmdiameter filter paper discs.

72 hours 96 hours Glucose (control) 18 16 I. lnoculum preparation a.First vegetative stage lnoculum source: Slant culture ofStreptosporangium Brasiliense grown on oatmeal agar. A medium andconditions of growth identical to those already described in Example -1are employed.

b. Second vegetative stage Inoculum source: 2.5 percent (25 milliliters)of the first vegetative stage. The medium used for the second vegetativestage is the same as the medium employed in the first stage. The medium,4 liters is a liter glass fermentor, is adjusted to pH 7.2-7.3,sterilized for 30 minutes at 121 C, inoculated and incubated at 28 C for72 hours.

During the incubation the broth is aerated at the rate of one liter ofair per liter of broth per minute and stirred at 800 rpm. At the end ofthe growth period the pH is 8.5 and a percent mycelium volume of 12percent is obtained.

II. Fermentation conditions Inoculum sources: 300 milliliters (7.5percent) of the second vegetative stage. The medium employed is the sameas described in Example I adjusted to pH 7.2 7.3 and sterilized for 30minutes at 121 C. The inoculated medium is incubated under the sameconditions used for the development of the second vegetative stage.Maximum antibiotic titers are usually obtained after 72 hours offermentation.

EXAMPLE 4 Extraction of Selenomycin from Fermentation Media Forty litersof culture broth are filtered at pH ,8.5 and the mycelial cake isdiscarded. The pH of the culture filtrate is lowered to 5.5 by additionof normal aqueous hydrochloric acid. Sodium chloride is added to aconcentration of percent (w/v). The filtrate is extracted twice withchloroform, a volume of chloroform equal to one-half the filtrate volumebeing employed for each extraction, and the chloroform extractsarecombined. The combined chloroform extracts are dried over sodiumsulfate, and concentrated to a volume of 50 rnilliliters in vacuo at C.The antibiotic is precipitated from the concentrated extract by theaddition of 2 liters of light petroleum. Four grams of crude antibioticare obtained. The crude antibiotic is suspended in 200 milliliters of amixture of 30 percent by volume of chloroform in benzene. The suspensionis shaken at a temperature of -40 C., the insoluble fraction is filteredoff, the filtrate is concentrated to a volume of 80 milliliters and 500milliliters of hexane are added. The precipitate is dissolved in 30milliliters of hot benzene and the hot solution is treated withcharcoal, filtered and cooled at C. for 10-12 hours. Eight hundred mg.of white amorphous product are obtained. The product is found to beactive against Staphylococcus aureus at a concentration of 0.2micrograms per rnilliliter.

EXAMPLE 5 Preparation of Acetylselenomycin 0.800 Grams of selenomycinare mixed with 20 rnilliliters of pyridine, and 20 grams of aceticanhydride are added to the mixture. The mixture is held at a temperatureof 20-25 C. for 24 hours after which the product is separated by pouringthe mixture into ice water. The acetylselenomycin product is purified bychromatography through a silicagel column by eluting with a methanolsolution containing 2 percent of chloroform. The compound afterrecrystallization from methanol is found to melt at l52-154 C.

What is claimed is:

l. The antibiotic substance, selenomycin, having a melting point of -l38C.; being soluble in lower alkanols, chloroform, ethyl acetate, acetone,dioxane and hot benzene and insoluble in diethyl ether; having anultraviolet absorption spectrum with the following maxima: in 0.1N HCl,shoulder at 245-257 mp. (15} 41), in pH 7.3 buffer solution, 295 my. Zn=in 0.1N NaOH, 295 m (El Z4.= ha ing an a id gr up with pKa 5.5; havingan infrared absorption spectrum in nujol with maxima at the followingwave-lengths expressed in cm: 3,400, 1,740, 1,650, 1,570, 1,550, 1,350,1,245, 1,200, 1,170, 1,100, 1,040, 1,000, 980, 950, 912, 870, 835, 812,783, 770, 738, 720, 680; giving positive Tollens and Fehling reactionsand negative Schiff, ferric chloride and Molisch reactions; decolorizingpotassium permanganate in neutral and acid solution; giving aphenylhydrazone with 2,4-dinitrophenylhydrazine; and giving a browncolor with concentrated sulfuric acid and concentrated hydrochloricacid; and being further characterized in that said selenomycin isadapted to be acetylated with acetic anhydride in pyridine to produceacetylselenomycin of melting point 152-154 C.; containing the elementscarbon, hydrogen, oxygen in substantiaTy the following proportions byweight: carbon 55.5 percent, hydrogen 4.86 percent and oxygen 38.8percent; containing the acetyl group in a proportion of about 21percent; showing specific rotatory power (a)D 3 (C=0.3 percent inmethanol); having an ultraviolet absorption spectrum with the followingmaxima: in 0.1N NaOl-l, 294 mu (131%,:60), in 0.1N HCl and in pH 7.3buffer solution, shoulder at 250-270 my; having an infrared absorptionspectrum in nujol at the following wavelengths expressed in cm": 3,400,1,790, 1,745, l,690-1,640, 1,545, 1,340, l,240-1,235, 1,195, 1,130,1,105, 1,080, 1,040, 980, 958, 920-914, 865, 840, 830, 780, 750, 735,700, 684.

3. The process of claim 2 wherein the source of carbon comprises amember of the group consisting of glucose, xylose and galactose.

4. The process of claim 2 further comprising the step of isolatingselenomycin from the medium.

2. A process useful for the manufacture of selenomycin, which comprisescultivating the organism Streptosporangium brasiliense ATCC No. 21393under aerobic conditions in an aqueous nutrient medium containing asource of carbon and of nitrogen and inorganic salts at a temperaturebetween about 25* and about 35* C. for a time sufficient to providesubstantial antimicrobial activity in the medium.
 3. The process ofclaim 2 wherein the source of carbon comprises a member of the groupconsisting of glucose, xylose and galactose.
 4. The process of claim 2further comprising the step of isolating selenomycin from the medium.